1. Field of the Invention
The present invention relates to an inkjet printer and a printing system, and a method of compensating for nozzle deterioration, and more particularly, to an inkjet printer and a printing system capable of preventing print quality deterioration due to defective nozzles by varying a printing workload share for each nozzle group, and a method of compensating for the nozzle deterioration.
2. Description of the Related Art
A printer prints print data onto a recording medium such as a paper. Inkjet type, laser type and thermal type printers are commonly available types of printers. An inkjet printer prints an image on a paper while a print head moves across an advancing direction of the paper, ejecting ink through nozzles. For higher printing speed and resolution, nozzles are formed on the print head of the inkjet printer in an increasing number.
FIGS. 1A and 1B show an example of nozzle arrangements, in which the nozzles 13 and 15 are arrayed on print heads 10 and 14 of the color inkjet printer. Characters ‘Y,’ ‘M,’ ‘C,’ and ‘K’ in the drawings respectively indicate nozzles through which ink of the colors Yellow, Magenta, Cyan, and Black, is respectively ejected.
In such an inkjet printing type printer, a size and ejecting direction of the ink droplet becomes different from the desired values during the manufacturing process and/or as time goes by. As a result, the image is incomplete due to defective nozzles, and does not meet the requirements of a user. This is especially true when the print head is driven to have one nozzle print one line. In such a case, line printed by the defective nozzle is more noticeably distorted.
In an attempt to deal with such deterioration of print quality due to defective nozzles, a Shingling approach has been suggested. According to the Shingling approach, the print head is driven to spread out the image which is printed by the defective nozzles. Also, according to the Shingling approach, the nozzles of identical numbers are grouped into a plurality of nozzle groups, each printing the same amount. This approach, however, has a shortcoming. That is, because the same amount of the printing workload is assigned to each nozzle group, each of which has the same number of nozzles, print quality deterioration cannot be properly dealt with when there are different numbers of defective nozzles in the nozzle groups.